Handhole plug



Feb. 15, 1966 E. P. WORTHEN ETAL 3,235,120

HANDHOLE PLUG Original Filed Aug. 22, 1960 ATTORNEY United States Patent 3,235,120 HANDHOLE PLUG Eugene Porter Worthen, Braintree, and John Henry Stelling, South Yarmouth, Mass., assignors, by mesne assignments, to Bethlehem Steel Corporation, a corporation of Delaware Original application Aug. 22, 1960, Ser. No. 51,043.

Divided and this application Mar. 8, 1965, Ser.

6 Claims. (Cl. 220-39) This application is a division of copending application Serial No. 51,043 filed August 22, 1960 for Tubesheetless Buttwelded U-Tube Type Combined Steam Generator and Non-Condensable Gas Extractor.

The present invention relates broadly to a plug for a header. More particularly, the present invention relates to a handhole plug for a pipe header.

As disclosed in the above-mentioned parent application Serial No. 51,043, the present invention is particularly useful in association with pipe headers in steam generators operating at high temperatures and pressures. Such steam generators may, for instance, receive primary saturated steam from a nuclear reactor of the boiling water type and raise secondary steam from feed heated by the primary steam, the secondary steam being used for example in power plants. These steam generators may receive primary saturated steam from the reactor at a pressure of 1000 p.s.i.a. (approximately 545 F.) to generate secondary saturated steam at a pressure of 600 p.s.i.a. (approximately 486 F.), the primary steam condensate leaving at about 545 F. and the secondary feed entering at about 486 F. These figures are given by way of illustration only. t,

Steam generators of the type above described have a number of tubes in which the high-temperature, high pressure heating medium (the primary saturated steam from the nuclear reactor) is circulated. As disclosed in the above-mentioned parent application Serial No. 51,043, these tubes may be fed from a header and may discharge to a header, replacing the conventional tube sheet. From time to time, while the steam generator is in service, leaks may occur in some of the tubes. For reasons of economy, it is desirable to be able to quickly secure access to the interiors of the defective tubes to plug them, thus removing the defective tubes from service and stopping leakage therethrough without taking the steam generator out of service for any extended period of time. Thereafter, when convenient, the defective tubes can be replaced with new tubes. Conventionally, handhole plugs in the headers opposite the tubes are provided. These handhole plugs are removed to obtain access to the interiors of their respec- \.ve tubes, and are replaced to close the header. One problem is to provide a handhole plug which can withstand the high pressure of the primary saturated steam in the header thereby to provide a seal in the header wall. Another problem is to provide a handhole plug which can be used in emergencies when special welding equipment is not available, to provide a seal in the wall of the header capable of withstanding the high pressure of the primary saturated steam in the header.

One of the objects of this invention is to provide an improved handhole plug.

Another object of this invention is to provide an improved handhole plug adapted to withstand high piFssures and yet capable of being quickly and easily removed and installed in a header.

Yet another object of this invention is to provide an emergency handhole plug and gasket, in the event seal welding facilities are not immediately available, capable of withstanding high pressures.

Other and further objects of this invention will become apparent during the course of the following description.

We have discovered that the foregoing objects can be attained by providing handhole plugs of special configuration.

Referring now to the drawing, in which like numerals represent like parts in the several views:

FIGURE 1 represents a transverse section of a header showing one form of handhole plug.

FIGURE 2 represents a longitudinal view of the header of FIGURE 1, partially broken away at the centerline, showing the same form of handhole plug.

FIGURE 3 represents a medial sectional view of another form of handhole plug, viz., the emergency handhole plug, and corresponds with a similar view of the first mentioned handhole plug of FIGURE 2.

When a tube 12 develops a defect, the openings in fourelement fittings 10 corresponding to the defective tube 12 can be plugged, permitting continued operation of the steam generator until such time as it is convenient to replace the defective tube 12. The present invention permits easy access through header 6 to the proper hole of the particular four-element fitting 10 for quick installation of a plug (not shown).

Header 6 is provided with a number of internally threaded collars 40 welded thereto, each of said collars 40 being located opposite a pair of four-element fittings 10 as shown in FIGS. 1 and 2. To close the openings in header 6, diaphragms 41 are sealed welded thereto at 42. Expansion ring 43 on diaphragm 41 prevents seal weld 42 from cracking as it cools. Handhole plug 13 is externally threaded to mate with collar 40, and when fully inserted, bears against diaphragm 41. Thus, in this design, tightness is maintained by diaphragm 41 and seal weld 42, and the holding power is provided by the handhole plug 13. Means (not shown) will be provided to prevent handhole plug 13 from unscrewing in service. To open the header 6 to gain access to the interior of any particular four-element fitting 10, handhole plug 13 is unscrewed, seal weld 42 is cut, and diaphragm 41 is removed.

In an emergency, when handhole plug 13 and diaphragm 41 have been removed from an opening in header 6, and seal welding facilities are not immediately available to reweld diaphragm 41 at 42 to header 6, emergency handhole plug 44 may be used.

Emergency handhole plug 44 comprises externally threaded head 45 mating with collar 40, gasket retaining ring 46 with circumferential lip 47 and integrally mounted to head 45 through intermediate resilient ring portion 48, and a gasket 49 retained by said gasket retaining ring 46 and circumferential lip 47 and adapted to seat on collar 40 as shown in FIG. 3. Preferably, circumferential lip 47 closely engages collar 40. Emergency handhole plug 44 further comprises a compression ring 50 slidably mounted to shaft 51 and adapted to bear against gasket retaining ring 46, a nut 52 threadedly mounted to threaded portion 53 and adapted to bear against compression ring 50, and a square-headed end 54 by means of which plug 44 can be threaded into header 6.

To use emergency handhole plug 44, threaded head 45 is screwed into collar 40 to bring gasket 49 to seat against collar 40, said head 45 not being screwed in to the extent that gasket 49 will be damaged by rotational friction. Then, nut 52 is screwed down on threaded portion 53 to force compression ring 50 against gasket retaining ring 46, thereby compressing gasket 49.

We claim:

1. Removable sealing means for an opening in a header comprising a plug, a first threaded end on said plug adapted to be screwed into said opening, a gasket retaining ring and a resilient intermediate ring portion securing said gasket retaining ring to said plug, a gasket supported by said gasket retaining ring and adapted to engage said pipe header about said opening, a compression ring slidably mounted to said plug and adapted to engage said gasket retaining ring, and means on said plug to force said compression ring adjacent said gasket retaining ring to compress said gasket about said opening.

2. Apparatus as in claim 1, said last mentioned means comprising a second threaded end on said plug, and a nut adapted to be screwed on said second threaded end to bear on said compression ring.

3. In combination with an opening in a header and an internally threaded collar secured to said header in registry with said opening, removable sealing means comprising a plug, a first threaded end on said plug adapted to be screwed into said collar, a gasket retaining ring, a

resilient intermediate ring portion securing said gasket 1 retaining ring to said plug, a peripheral lip about said gasket retaining ring closely engageable with said collar, a gasket supported by said gasket retaining ring and said peripheral lip and adapted to engage said collar, a compression ring loosely mounted to said plug and adapted to engage said gasket retaining ring, and means on said plug to force said compression ring against said gasket retaining ring to compress said gasket against said collar.

4. Apparatus as in claim 3, said last mentioned means comprising a second threaded end on said plug, and a nut adapted to be screwed on said second threaded end to bear on said compression ring.

5. In combination with an opening in a header and'an internally threaded collar secured to said header in mg istry with said opening, removable sealing means comprising:

(b) a first threaded end on said plug adapted to be screwed into said collar,

(c) sealing means resiliently mounted to said plug and adapted to engage said collar around the periphery of said opening,

(d) a compression ring loosely mounted to said plug and adapted to engage said sealing means, and

(e) means on said plug to force said compression ring against said sealing means to compress the same against said collar.

6. Apparatus as in claim 5, said last-mentioned means comprising:

(a) a second threaded end on said plug, and

(b) a nut adapted to be screwed on said second threaded end to bear on said compression ring.

References Cited by the Examiner UNITED STATES PATENTS 2,863,647 12/1958 Tinker 220-39 3,076,578 5/1960 Smith 22046 THERON E. CONDON, Primary Examiner. 

1. REMOVABLE SEALING MEANS FOR AN OPENING IN A HEADER COMPRISING A PLUG, A FIRST THREADED END ON SAID PLUG ADAPTED TO BE SCREWED INTO SAID OPENING, A GASKET RETAINING RING AND A RESILIENT INTERMEDIATE RING PORTION SECURING SAID GASKET RETAINING RING TO SAID PLUG, A GASKET SUPPORTED BY SAID GASKET RETAINING RING AND ADAPTED TO ENGAGE SAID PIPE HEADER ABOUT SAID OPENING, A COMPRESSION RING SLIDABLY MOUNTED TO SAID PLUG AND ADAPTED TO ENGAGE SAID GASKET RETAINING RING, AND MEANS ON SAID PLUG TO FORCE SAID COMPRESSION RING ADJACENT SAID GASKET RETAINING RING TO COMPRESS SAID GASKET ABOUT SAID OPENING. 